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St Louis Water Guy Doesn’t Know How Sinkhole That Ate a Car Formed, So Let’s Find Out

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All right, everybody, break out your spiral-bound notebooks and prepare your best “Yeah, I’m totally paying attention” faces, because it’s time to learn something, here.

I was looking about the internet this morning when I came across a story out of St. Louis. A man and his girlfriend parked their car on the street, only to come back later to find that instead of a car on the street, they now owned a car  that was upside-down in a huge sinkhole. Here’s a video of the scene from the Associated Press:

For those of you unable or unwilling to play that video, here is a still image:

That is just plain not good, although thankfully nobody was hurt. However, what really struck me was that the AP then spoke to Vincent Foggie, a decorated employee of the city’s water division, who said that the hole was missing a large amount of dirt (which, of course, would normally be what holds up the road), which he said was rare in the city. He then added, “We don’t know what happened. I have no idea where the dirt went.”

Although it seems to me that Foggie should probably know what happens to form a sinkhole (since that’s a water issue), we can inform both him and you all at the same time.

Basically, sinkholes form due to moving water.

In areas where a lot of the bedrock is made of limestone or similar rock, moving groundwater could gradually open a cave, letting more and more dirt fall down inside until the void reaches the surface. This is a possibility here, as St. Louis sits on lot of limestone. However, based on that pipe spewing water into the hole, I think that we can take a different guess.

Sinkholes can also form in a more artificial way if a gap forms in a water pipe or it becomes damaged, as the water flow washes away the dirt over time. Here is a demonstration from Practical Engineering (I skipped to 4:06 in the video to show the case I am talking about).

The AP noted that an 8-inch water main at the site (presumably the pipe spewing water, there) appeared to have been broken for some time. This would be more than enough to, over time, wash away the supporting soil until the support of the pavement was simply not enough.

Neat, huh?

News Sources: Associated Press via Yahoo News, Practical Engineering via YouTube, St Louis Water Division, Washington University in St. Louis